Diaphragm for sound-conveying instruments



News, 1923. 1,472,830 Y J. A. HACKER DIAPHRAGM FOR SOUND CONVEYING INSTRUMENTS I Filed Jan. 5, 1921 Patented a... e, 1923.

UNITEDTSTA'ILES PATENT OFFICE.

:rosnrnos A. nacxsn,

OF CHICAGO, ILLINOIS.

I marnnaem :ron sounn-colvvnrmc INSTRUMENTS.

Application filed January 3, 1921. Serial No. 434,428.

scription, reference being had to theaccompanying drawing, forming a part of this specification.

This invention relates to diaphragms for sound-conveying.instruments and the process of making these diaphragms, and more particularly to acoustic reproduction diaphragms for talking machines, telephones, dictagraphs, and the like.

One of the objects of this invention resides, therefore, in the production of a dia-' phragm and the process for producing said diaphragm which will give a fuller tone, greater 'depth of tone and finer acoustics, and give a true reproduction of either the voice or instruments, and which will at the same time eliminate most of the objectionable features now found in the ordinary commercial metal and mica disc diaphragms. These results are obtained by making the improved diaphragm of a porous or cellular. material, preferably fiber, the diaphragm so constructed being thoroughly imregnated and coated with a solution of celulose. The impregnation and the coating of the diaphragm renders it impervious to 35 moisture and renders it free from the effects of climatic changes. It also produces a diaphragm .which gives a truer reproduction and which gives aclear, loud, full and distinct tone and also substantially eliminates all discordant noises, such as scratchin etc. A diaphragm made in accordance wit the teachings of thisinvention will truly re produce the most delicate sounds with softness and clear and distinct volume.

' Another object of the invention resides in the physical shape of the diaphragm thus constructed, whereby-a truer reproduction of voice or instruments will be further enhanced.

come apparent from the'followingdescri tion. the accompanying drawings and t e appended claims.

For the pur ose of description, the accompanying ilustrations are included,'

solution is preferably prepared b Other objects of the; invention will be-- which show preferred forms of diaphra'gms,

which diaphragms, in order togive the best results, should be constructed and treated as hereinafter described. In the drawings- Fig. 1 represents a plan disc diaphra Fig. 2 shows a .disc diaphragm wit a compressed and hardened center;

Fig. 3 shows a disc diaphragm having a depressed and hardened center as Well as a depressed and hardened circumferential ring on one face of the disc, the other face of the disc being flat;

Fig. 4 shows a diaphragm having a de- I pressed and hardened center and a circumferential compressed and hardened rin the compression being applied so as to o tain a depression on either side of the diaphragm; and

Figs. 5, 6, 7 and 8 are transverse sections of the discs illustrated in Figs. 1, 2, 3 and 4., respectively.

The diaphragms shown in the illustrations are preferably made by my improved process. This process may be racticed in a number of ways, the two pre erred ways being described in the following.

One manner of practicing this process consists in making a solution of cellulose and then mixing in this solution the material-preferably fiber-from which the diaphragm is to be constructed. The preferred solution of cellulose in which the dlaphra material is impregnated is obtained by issolving nitro-cellulose in a solvent containing equal parts of alcohol and ether. To this solution a small quantity of acetanilide is added for hardening purposes, as well as a small amount of boracic acid which serves as a fireproofing agent. Obviously, any other suitable form of cellulose, as well as the solvent therefor, couldbe utilized, and likewise other forms of hardening and fireproofing material could be substituted for the acetanilide and the boracic acid. The dissolving 1 pound of nitro-c lulose in t e alcohol and ether solvent- The amount of solvent necessary will depenl upon the viscosit I of the solution which is ultimately desired. When 1 pound of nitro-cellulose is thus dissolved, 1 ounce of acetanilide and 1 ounce of preferably added. The

boracic acid are amount of acetanihde'and boracic acid may be-varied, however, depending upon the degree of hardness which is ultiri'iately desired and the amount of fireproofing material which it is deemed necessary to include in the solution. The figures given above as to the amounts of the materials used to obtain the cellulose solution may all be varied, the proportions depending upon the desired viscosity of the ultimate solution. In using the impregnating material, it is desirable to use an initial solution which is comparatively light in viscosity and density and to use for the final impregnation a solution of substantially greater density and viscosity. A plurality of solutions of varying densities and viscosities can also be used, the material which is being immersed or impregnated being successively dipped in these various solutions of increasing density and viscosity. The material after each dipping should be thor ughly dried before immersing in the next solution of greater density. The material which is placed in this solution of cellulose mustbe thoroughly disintegrated before it is placed in the solution, and enough of this material should be added so as to give the mixture the proper density which is desired. Ordinarily the density of this solution should be such as to represent a thick pasty solution. After this mixture has been prepared it is poured into molds of the desired shape and then compressed, so as to obtain a finished article of the sha e desired. The compression of this mixture in the molds will result in a finished diaphragm which is thoroughly impregnated with the solution of cellulose and which will have an exterior surface or shell of somewhat glossy appearance composed of the hardened and dried solution of cellulose.

The diaphragms are preferably made in another .:anner, as, for example, by using a plurality of sheets of the material such as fiber, paper, etc., from which the diaphragm is to be constructed and immersing these sheets in the solution of cellulose. The sheets, after being so immersed, are then stacked one on top of the other until the proper thickness of diaphragm is obtained after which the assembled sheets are given another immersion in the impregnating solution. This solution in which the assembled sheets are impregnated is preferably a solution of substantially greater viscosity and density than the solution used for the impregnation of the individual sheets prior to the time that they are stacked one on top of the other to form the assembled diaphragm. Obviously, as hereinbefore described, the sheets should be thoroughly dried between the immersions; likewise, if

desired. instead of subjecting the sheets to but two immersions, they may be subjected ;to a plurality of immersions in solutions of increasing viscosity and density as hereinbefore set out. The diaphragm constructed of the assembled sheets, the individual sheets of which were individually immersed in a light solution of cellulose, and the assembled sheets of which were immersed in a solution of greater viscosity and density is placed in a mold and compressed to obtain the desired form. The non-aqueous solution of cellulose i both of these described processes acts as a waterproofing to render the diaphragm imperviou to moisture, and also functions as a cement to thoroughly bind together the particles from which the diaphragm is constructed.

In the process of making the diaphragms of sheets. obviously the sheets may be treated to the solution of cellulose by flowing the solution on the sheets or by applying it with a brush, but the immersion process is the preferable one.

In making diaphraglns of this character, fiber is the preferable material used, but any porous or cellular material capable of absorbing the solution of cellulose could obviously be used.

Referring to the illustrations, Fig. 1 is a plain disc diaphragm made according to this improved process, and consists of the circular disc 8 fitted with the central hole 9 to receive the arm from the reproduction needle. The disc should be thoroughly impregnated with the solution of cellulose, as above described, and then compressed. Due to this operation the disc will have an exterior glossy surface or shell 10 composed of the dried and hardened non-aqueous solu- 100 tion.

Fig. 2 represents a second form of disc treated in the same manner and comprises the disc 11 having the compressed central portion 12 and the perforation 13 to receive 105 the arm from the reproduction needle. The central compressed portion 12 is considerably harder than the outer portion 14 and thus gives a suitable surface for properly attachmg the arm from the reproduction needle. 110 The disc 11 likewise has an outer shell 15 of the compressed and dried solution of cellu lose.

Fig. 3 shows another form of diaphragm comprising the disc 16 having a compressed 115 outer ring 17, a compressed center 18 and an intermediate non-compressed ring 19. The central compressed portion is fitted with the perforation 20 to receive the arm from the reproduction needle.

Fig. 4 illustrates another form of diaphragm, similar to the diaphragm illustrated in Fig. 3 with the exception that the depressions shown on.but one side of the diaphragm in Fig. 3 are extended to both 118 sides of the diaphragm in Fig. 4. Thus in this figure the disc 21. comprises the compressed circumferential ring 522 and the compressed central ring 23 fitted with the central perforation 24 to receive the arm from the III reproduction needle. Intermediate between anyof the forms illustrated, when treated according to the new process as herein described, give results which are very much superior, in quality of tone and trueness' of reproduction, to any of the commercial forms of mica and metallic discs.

Obviously this invention is not limited to the specificembodiment thereof herein illustrated and described, but other forms and variations and other applications are included within its spirit and scope, as set out in the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is!

1. As a new article of manufacture, an acousticjdiaphragm consisting of a cellular material impregnated in a solution of cellulose said diaphragm having a small portion of greater density'than the remainder of the diaphragm.

2. As a new article of manufacture, an acoustic diaphragm comprised of cellular material impregnated in a solution of cellulose, said diaphra in having a depressed central portion har er than the remainder of the diaphragm.

3. As a new article of manufacture, an acoustic diaphragm consisting of a plurality of sheets of material impregnated in a solution of cellulose, said sheets of material being assembled one on top of the other, and the assembled sheets being impregnated in a solution of cellulose of greater viscosity and density than said first mentioned solution, said assembled sheets, after said second impregnation, being compressed in a mold to obtain the desired physical contour of the diaphragm.

In witness whereof I have hereunto subscribed my name.

J OSEPHUS A. HACKER. 

